1. Field of the Invention
The present invention relates to a nonlinear optical microscope apparatus, and more particularly, to a nonlinear optical microscope apparatus used to observe a living sample.
2. Description of the Related Art
In recent years, in vivo imaging for observing a living organism alive has been actively studied to elucidate biofunctions. For in vivo imaging, diverse nonlinear optical microscopes using a nonlinear optical phenomenon, such as a multi-photon excitation microscope and the like, are used.
Also in nonlinear optical microscopes as well as other microscopes, it is desirable to make a laser beam incident to an objective so that a pupil of the objective is filled in order to implement a high resolution by fully taking advantage of performance of a nonlinear optical microscope. In the meantime, it is desirable to make the laser beam incident to the objective in a state where a beam diameter is slightly smaller than a pupil diameter of the objective in order to obtain a brighter image.
As described above, it is conventionally known that brightness and a resolution are varied by changing a beam diameter with respect to a pupil diameter of an objective. A technique related to this fact is disclosed, for example, by Japanese Laid-open Patent Publication No. 2010-096813.
Japanese Laid-open Patent Publication No. 2010-096813 discloses simulation results such that an intensity of fluorescence exhibits a peak when a normalized beam diameter (a beam diameter/a pupil diameter of an objective) is approximately 0.8 in a two-photon excitation microscope apparatus.